Process for preparing organic hydroperoxide containing product

ABSTRACT

Process for preparing alkylaryl hydroperoxide containing product, which process comprises:
     (a) oxidation of an alkylaryl compound to obtain reaction product containing alkylaryl hydroperoxide,   (b) contacting with water at least part of the alkylaryl hydroperoxide containing reaction product obtained in step (a) which reaction product contains less than 0.05 % wt of sodium,   (c) separating the product of step (b) into a hydrocarbonaceous phase containing alkylaryl hydroperoxide and an aqueous phase,   (d) optionally repeating process steps (b) and (c) one or more times,   (e) contacting at least part of the hydrocarbonaceous phase containing alkylaryl hydroperoxide obtained in step (c) or (d) with olefin and catalyst to obtain alkylaryl hydroxide and oxirane compound, and   (f) separating at least part of the oxirane compound from the alkylaryl hydroxide.

This is a division of application Ser. No. 10/359,952 filed Feb. 6,2003, now U.S. Pat. No. 6,700,005 the entire disclosure of which ishereby incorporated by reference

The present invention relates to a process for preparing alkylarylhydroperoxide containing product. Such product is suitable for use invarious processes, such as in the preparation of oxirane compounds andin the preparation of alkenyl aryl.

BACKGROUND OF THE INVENTION

Processes for preparing propylene oxide employing alkylarylhydroperoxide compounds, are well known in the art. As described in U.S.Pat. No. 5,883,268, such processes conventionally comprise peroxidationof ethylbenzene, followed by contacting the peroxidation reactionproduct with aqueous base in amount sufficient to neutralize acidiccomponents thereof and separating the resulting mixture into an aqueousstream and a deacidified organic stream. The base contaminated,deacidified hydroperoxide stream is washed with water and the resultingmixture separated into an organics contaminated water phase and anorganic phase having a reduced alkali metal content.

It has now been found that the peroxidation reaction product does notneed to be washed with aqueous base. Surprisingly, the peroxidationreaction product can be washed with water only. An important advantageof the absence of a wash with aqueous base is that a larger amount ofaqueous phase is allowable in the organic phase. The larger amount ofaqueous phase is acceptable in the process according to the presentinvention as such aqueous phase will not contain aqueous base residuesuch as sodium salts. The presence of such compounds generally causesthe problems in subsequent process steps. Water does not need to berigorously removed in the process of the present invention and thismakes that the separation of water and organic phase can be carried outin a more simple way. Furthermore, upsets in the plant leading to lessefficient water removal are more acceptable in the present inventionthan they are in a conventional process.

It was found that alkylaryl hydroperoxide containing reaction productwhich was washed with water only, gave similar catalyst deactivation ina subsequent reaction as product washed with both aqueous base andwater, while a higher yield of alkylaryl hydrogen peroxide was observedwhen the reaction product had been washed with water only. The latter isattributed to reduced decomposition of alkylaryl hydrogen peroxide. Suchdecomposition is thought to be catalysed by the presence of aqueous baseat basic conditions. The similar deactivation is very surprising as awater wash removes very little contaminants such as benzoic acid, whichare known to be present in the crude reaction product. Furthermore, lessemulsion was observed to be formed when the alkylaryl hydroperoxidecontaining product was washed with water only.

WO 00/12470 describes a process for purifying a cyclohexyl hydroperoxidecontaining reaction mixture in order to make it suitable fordecomposition or hydrogenation into cyclohexanol and cyclohexanone. Thisdocument contains no information on purification of an akylarylhydroperoxide containing reaction mixture to be reacted with olefin inthe presence of an epoxidation catalyst.

SUMMARY OF THE INVENTION

Surprisingly, a process has now been found which gives an improvedalkylaryl hydroperoxide containing product.

The process for preparing organic hydroperoxide containing productaccording to the present invention comprises:

-   (a) oxidation of an alkylaryl compound to obtain reaction product    containing organic hydroperoxide,-   (b) contacting with water at least part of the alkylaryl    hydroperoxide reaction product obtained in step (a) which reaction    product contains less than 0.05% wt of sodium,-   (c) separating the product of step (b) into a hydrocarbonaceous    phase containing the alkylaryl hydroperoxide and an aqueous phase,-   (d) optionally repeating process steps (b) and (c) one or more    times,-   (e) contacting at least part of the hydrocarbonaceous phase    containing alkylaryl hydroperoxide obtained in step (c) or (d) with    olefin and catalyst to obtain alkylaryl hydroxide and oxirane    compounds, and-   (f) separating at least part of the oxirane compound from the    alkylaryl hydroxide.

The product subjected to step (b) is considered to be the product intotal. If any aqueous phase is present in the reaction product to besubjected to the water wash, the sodium content of this aqueous phase istaken into account as well. A conventional alkylaryl hydroperoxidecontaining product which has been neutralised with aqueous base, willgenerally contain of from 0.10 to 0.15% wt of sodium, based on totalamount of both organic and aqueous phase, before it is subjected to awater wash.

It is preferred that water is removed from the hydrocarbonaceous phasecontaining alkylaryl hydroperoxide obtained in step (c) or (d) beforethis hydrocarbonaceous phase is subjected to step (e). A convenient andpreferred method for removing water from this hydrocarbonaceous phase isdistillation.

The alkylaryl hydroxide obtained in step (f) can be used in a wide rangeof processes. Such process is preparing an alkenyl aryl by dehydratingthe alkylaryl hydroxide. Another process is hydrogenating the alkylarylhydroxide to obtain an alkyl aryl. Therefore, the process according tothe present invention suitably comprises further:

-   (g) converting at least part of the alkylaryl hydroxide obtained in    step (f). Generally, the conversion produces reaction product and    water.

Preferably, step (g) comprises either dehydration or hydrogenolysis ofthe reaction product. Hydrogenolysis is the reaction of the alkylarylhydroxide with hydrogen, preferably in the presence of catalyst.Dehydration will generally produce an alkenyl aryl and water, whilehydrogenolysis will generally produce alkylaryl. Preferably, thehydrogenolysis will produce the alkylaryl used as starting compound.

DETAILED DESCRIPTION OF THE INVENTION

Alkylaryl compounds which are most preferably used in the process of thepresent invention are benzene compounds containing at least 1 alkylsubstituent which alkyl substituent contains of from 1 to 10 carbonatoms, preferably of from 2 to 8 carbon atoms. Preferably, the benzenecompound contains-on average of from 1 to 2 constituents. The alkylarylcompounds most frequently encountered are ethylbenzene, cumene anddi(iso-propyl) benzene.

The oxidation of the alkylaryl compound can be carried out by anysuitable process known in the art. The oxidation can be carried out inthe liquid phase in the presence of a diluent. This diluent ispreferably a compound which is liquid under the reaction conditions anddoes not react with the starting materials and product obtained.However, the diluent can also be a compound necessarily present duringthe reaction. For example, if the alkylaryl is ethylbenzene the diluentcan be ethylbenzene as well and if the alkylaryl is cumene the diluentcan be cumene as well.

Besides the desired alkylaryl hydroperoxide, a range of contaminants arecreated during the oxidation of organic compounds. Although most ofthese are present in small amounts, it has been found that the presenceof compounds such as organic acids can cause problems in further use ofthe alkylaryl hydroperoxides. As described in U.S. Pat. No. 5,883,268,the conventional method of reducing the amount of contaminants is bycontacting the reaction product containing alkylaryl hydroperoxide withan aqueous alkali solution. However, contact with the aqueous alkalisolution introduces alkali metal into the hydroperoxide containingreaction product. Although the amount of organic acids present in thehydroperoxide containing product can be decreased by the alkali wash,the amount of alkali metal contaminants is increased.

It has now been found that a simple water wash is more efficient inpurifying reaction product containing hydroperoxide than a treatmentwith aqueous base followed by a water wash. According to the presentinvention, the hydroperoxide containing product preferably is notcontacted with aqueous base, more specifically sodium hydroxide, betweenthe time at which it is produced by oxidation of organic compound andthe time at which it is reacted further.

Aqueous base most often used in conventional processes, are sodiumand/or potassium containing bases such as sodium hydroxide, potassiumhydroxide, sodium carbonate and potassium carbonate. Decomposition ofhydroperoxide is thought to be catalysed by the presence of these saltsat basic conditions. Therefore, it is preferred that the product sent tostep (b) contains less than 0.010% wt of sodium, preferably less than0.005% wt of sodium, more preferably less than 0.002% wt of sodium, mostpreferably less than 0.001% wt of sodium. The amount of sodium is theweight amount of metallic or ionic sodium on total amount of product,including both the organic phase and any aqueous phase which might bepresent. Furthermore it is preferred that the product sent to step (b)contains less than 0.050% wt of potassium, preferably less than 0.010%wt of potassium, most preferably less than 0.002% wt of potassium. Theamount of potassium is the weight amount of metallic or ionic potassiumon total amount of product, including both the organic phase and anyaqueous phase which might be present.

The reaction product of step (a) can be sent to step (b) as such.However, it is preferred to remove light compounds from the reactionproduct obtained. These light products can be removed by subjecting thereaction product of step (a) to distillation, preferably distillation atreduced pressure. A distillation which is especially suitable isso-called flash distillation, which comprises distillation at very lowpressure. It has been found that such flash distillation is efficient inremoving light compounds such as oxygen and light acids formed duringthe oxidation.

In the process according to the present invention, the reaction productof step (a) is contacted with water. The water which can be used cancontain contaminants, such as organic compounds. Such contaminants canhave been introduced by the recycle of at least part of the wash water,either to the same wash step or to another wash step. The water can befresh water only, it can be a combination of fresh water containingsubstantially no contaminants and one or more different waste waterstreams, or it can consist only of different kinds of waste waterstreams or it can consist of a single type of waste water.

The speed by which the equilibrium is reached in which contaminants areremoved as far as possible, can be increased in the ways known tosomeone skilled in the art. The contact between the reaction productcontaining alkylaryl hydroperoxide and water can be improved by intensecontact of the hydroperoxide containing reaction product and water. Suchintense contact can be achieved in any way known in the art, for exampleby intense mixing. However, a conventional water wash will suffice formost processes according to the present invention.

The exact conditions under which the water wash is carried out, stronglydepend on further circumstances. Preferably, the water wash is carriedout at a temperature of between 0° C. and 150° C., more preferably ofbetween 20° C. and 100° C.

In step (c), the product of step (b) is separated into ahydrocarbonaceous phase and an aqueous phase. A preferred methodcomprises allowing the hydrocarbonaceous phase and aqueous phase tosettle in a settling vessel and subsequently separating ahydrocarbonaceous phase from an aqueous phase. The hydrocarbonaceousphase containing alkylaryl hydroperoxide can subsequently be sent to acoalescer where further aqueous phase is removed. Preferably, step (c)is carried out at a temperature of between 0° C. and 150° C., morepreferably of between 20° C. and 100° C.

Further water, unconverted organic compounds and contaminants can beseparated by distillation from the hydrocarbonaceous phase obtained fromthe coalescer. Generally, the distillate contains unconverted organiccompounds, water and contaminants. The distillate obtained cansubsequently be phase separated in a vessel to obtain an organic phaseand an aqueous phase. The aqueous phase obtained in this way, willcontain organic contaminants and can be used as water for washingalkylaryl hydroperoxide containing reaction product.

Water which can be used in the present invention is water previouslyused in washing a hydrocarbonaceous phase containing alkylarylhydroperoxide. Preferably, such water is obtained by contacting ahydrocarbonaceous phase containing alkylaryl hydroperoxide with anaqueous phase, preferably clean water, and subsequently separating theaqueous phase from the hydrocarbonaceous phase. The aqueous phase soobtained can be used without further treatment.

As mentioned above, a very thorough separation of aqueous phase andhydrocarbonaceous phase is generally not necessary in the process of thepresent invention. Therefore, steps (b) and (c) preferably consist ofcontacting the reaction product containing organic hydroperoxideobtained in step (a) with water in an extraction column. Morepreferably, the extraction column is operated in counter current mode.

Waste water streams which might be used as part or total of the water instep (b) of the present process, are prepared in several ways in theprocess according to the present invention. Preferred waste waterstreams for use as water for use in the present invention contain atleast part of one or more of the following waste water streams: wastewater produced as by-product in the oxidation of alkylaryl compound instep (a), waste water obtained in cleaning filters for off-gas, aqueousdistillate obtained by distillation of hydrocarbonaceous phase obtainedin step (c) and water obtained in converting alkylaryl hydroxide in step(g). These streams are being discussed in more detail herein below.

In the oxidation of the alkylaryl compound, it has been observed thatwater can be produced. It is thought that this water originates fromside-reactions such as the decomposition of hydroperoxide. A waste waterstream which can be used in step (b) can be recovered by condensation ofthe reactor offgas, and separating the hydrocarbonaceous phase.

In the oxidation of the organic compound, off-gas is produced containingorganic contaminants. One of the possibilities to clean this off-gas, iswith the help of a filter, more specifically a charcoal filter. Thefilter has to be cleaned regularly to remove the absorbed contaminants.Usually, this is done with the help of water optionally containing smallamounts of further compounds. It has been found that such waste waterobtained in cleaning filters for off-gas is especially suitable for useas water in step (b).

Another waste water stream which has been found suitable for use aswater for step (b), is aqueous distillate obtained by separatinghydrocarbonaceous phase from aqueous phase, distilling thehydrocarbonaceous phase and subsequently separating thehydrocarbonaceous distillate from the aqueous distillate. Preferredembodiments for preparing such aqueous distillate for use as waste waterin step (b) have been described above in the discussion of step (b).Such aqueous distillate is especially suitable for use as water in step(b). Generally, the conversion process produces reaction product andwater.

A further stream which is especially suitable for use as water is thewater obtained in the conversion of alkylaryl hydroxide of step (g). Asmentioned above, the conversion preferably is dehydration orhydrogenolysis. If step (g) comprises dehydration, the product of thedehydration is preferably distilled whereby the distillate obtainedcontains water and organic compounds. This distillate is phase separatedby separating off hydrocarbonaceous phase in a settler and sending theaqueous phase to a coalescer. The aqueous phase obtained in thecoalescer can very suitably be used as waste water in step (b). If step(g) comprises hydrogenolysis, the water produced can be used as water instep (b), preferably after the hydrocarbonaceous phase has beenseparated off by phase separation. If the hydrogenolysis gives thealkylaryl compound used as starting product, the alkylaryl compoundobtained in step (g) is suitably recycled to step (a).

In process step (e), at least part of the hydrocarbonaceous phasecontaining alkylaryl hydroperoxide obtained in step (d) is contactedwith olefin, preferably propene, in the presence of a catalyst to obtainalkylaryl hydroxide and oxirane compounds. A catalyst which can suitablyused in such process comprises titanium on silica and/or silicate. Apreferred catalyst is described in EP-A-345856. The reaction generallyproceeds at moderate temperatures and pressures, in particular attemperatures in the range of from 0 to 200° C., preferably in the rangefrom 25 to 200° C. The precise pressure is not critical as long as itsuffices to maintain the reaction mixture as a liquid or as a mixture ofvapour and liquid. Atmospheric pressure may be satisfactory. In general,pressures can be in the range of from 1 to 100×105 N/m².

The reaction product of step (c) or (d) is preferably subjected todistillation before being used in step (e). The distillation removeslight products such as water which can be harmful to a subsequentcatalyst.

The oxirane compounds can be separated from the reaction productcontaining alkyl aryl hydroxide in any way known to be suitable tosomeone skilled in the art. The liquid reaction product may be worked upby fractional distillation, selective extraction and/or filtration. Thesolvent, the catalyst and any unreacted olefin or alkylarylhydroperoxide may be recycled for further utilization.

The alkylaryl hydroxide obtained in the process can be dehydrated in thepresence of a catalyst to obtain styrene and water. Processes which canbe used for this step have been described in WO 99/42425 and WO99/42426. However, any suitable process known to someone skilled in theart can in principle be used.

The present invention is further illustrated by the following examples.

EXAMPLE 1

In a reactor, air was blown through ethylbenzene. The product obtainedcontained ethylbenzene hydroperoxide.

To 200 grams of this product of room temperature was added 800 grams ofdemineralized water, and the combination was mixed for 1 hour.Subsequently, the mixture was allowed to settle overnight and was phaseseparated. The organic phase obtained was distilled at 30 mbar and50–55° C. The product obtained is called “water washed feed”.

COMPARATIVE EXAMPLE 1

Another part of the product containing ethylbenzene hydroperoxideprepared in Example 1, was contacted with a solution containing 0.5% wtNaOH in water and mixed at a temperature of 60° C. The weight ratio ofproduct containing ethylbenzene hydroperoxide to NaOH containingsolution was 4.5:1 (wt:wt). The neutralized mixture obtained was allowedto settle and was subsequently phase separated into a neutralizedhydrocarbonaceous phase containing ethylbenzene hydroperoxide and anaqueous phase. The neutralized hydrocarbonaceous phase containingethylbenzene hydroperoxide was subsequently washed twice with water. Theproduct obtained is called “neutralised and washed feed”.

COMPARATIVE EXAMPLE 2

A further part of the product containing ethylbenzene hydroperoxideprepared in Example 1, was distilled at 30 mbar and 50–55° C. Theproduct obtained is called “non-washed feed”.

EXAMPLE 2

Each of the above feeds prepared in Example 1, Comparative example 1 andComparative example 2 contained 35% wt of ethylbenzene hydroperoxide,and were tested in the following way. A feed solution was prepared bymixing 340 g 1-octene, 200 g of ethyl benzene hydroperoxide solution inethylbenzene and 400 g of ethyl benzene. The ethyl benzene hydroperoxideconcentration was determined by titration of an aliquot of the feed. A100 ml round bottom flask equipped with a condensor and a stirrer barwas charged with 50 ml of the feed solution and 1.00 g of catalyst. Thecatalyst contains titanium on silica and was prepared as described inthe Example according to the teaching of EP-A-345856. The flask wasimmersed in a 40° C. oil bath while the contents was stirred. After 1hour, the ethyl benzene hydroperoxide concentration was determined bytitration of an aliquot of the reaction mixture. The ethylbenzenehydroperoxide conversion was calculated as the amount of ethylbenzenehydroperoxide converted divided by the amount of ethylbenzenehydroperoxide converted when using the neutralised and washed feed. Theresults obtained are given in Table 1.

TABLE 1 ethylbenzene hydroperoxide conversion (relative) non-washed feed0.81 water washed feed 0.97 neutralised and washed feed 1.00 (bydefinition)

COMPARATIVE EXAMPLE 3

This experiment was carried out in a 1 liter jacketed reactor equippedwith a turbine stirrer, temperature control device and heating oil batchsystem. The reactor was charged with 561.2 g. of a solution containing26.34% wt of ethylbenzene hydroperoxide in ethylbenzene. This solutionwas heated to 70° C. After the extraction temperature was reached about300 ml of a caustic solution was added in one shot. The caustic solutionconsisted of demineralised water containing 6.8% wt sodium benzoate and0.4% wt sodium hydroxide. The caustic solution was preheated to the sametemperature in a separate vessel before being added to the organicphase.

After mixing for 15 minutes, the organic phase was separated andanalysed for ethylbenzene hydroperoxide content by iodometric titration.The ethylbenzene hydroperoxide content was found to be 25.72% wt.

EXAMPLE 3

The experiment of Comparative example 3 was repeated differing only inthat this time the organic phase was mixed with demineralised wateronly.

After mixing for 15 minutes, the organic phase was separated andanalysed for ethylbenzene hydroperoxide content by iodometric titration.The ethylbenzene hydroperoxide content was found to be 26.07% wt.

1. A process for preparing an alkenyl aryl, which process comprises:preparing an alkylaryl hydroxide containing product, by a processcomprising: (a) oxidating an alkylaryl compound to obtain reactionproduct containing alkylaryl hydroperoxide; (b) contacting with water atleast part of the alkylaryl hydroperoxide containing reaction productobtained in step (a) which reaction product contains less than 0.05% wtof sodium; (c) separating the product of step (b) into ahydrocarbonaceous phase containing alkylaryl hydroperoxide and anaqueous phase; (d) optionally repeating process steps (b) and (c) one ormore times; (e) contacting at least part of the hydrocarbonaceous phasecontaining alkylaryl hydroperoxide obtained in step (c) or (d) witholefin and catalyst to obtain alkylaryl hydroxide and oxirane compound;(f) separating at least part of the oxirane compound from the alkylarylhydroxide; and, dehydrating at least part of the alkylaryl hydroxideobtained in step (f) to an alkenyl aryl.
 2. The process of claim 1 whichprocess further comprises distilling the product obtained in step (c) or(d), and sending to step (e) hydrocarbonaceous phase from which lightcompounds have been distilled off.
 3. The process of claim 2 in whichprocess steps (b) and (c) are carried out in an extraction column. 4.The process of claim 3 in which process the product sent to step (b)further contains less than 0.05 wt % of potassium.